Current technologies used to study cell contractile forces include traction force microscopy (TFM) of substrates having embedded fluorescent particles. In TFM, cells are cultured as a monolayer on the surface of a thin substrate with fluorescent microspheres (e.g., latex beads) embedded therein. In another method, microfabricated silicone elastomeric post arrays have been developed for measuring the traction forces of adherent cells. See e.g., Sniadecki et al., Microfabricated Silicone Elastomeric Post Arrays for Measuring Traction Forces of Adherent Cells, Methods in Cell Biology, Vol. 83 (2007). In this method a vector map of traction forces is obtained by measuring the deflection of each micropost. Cellular contractile forces can also be measured indirectly by atomic force microscopy (AFM). AFM has been used to measure stiffness of cell cytoskeleton, which is broadly correlated to contractility through myosin contraction of the actin cytoskeleton. These approaches have been used to map stem cells, and correlated to the metastatic potential of cancer cells. Elastomeric micropillars have been used to track the contractility of stem cells, and researchers have found variation in contractility during differentiation. See J. Fu, et al., Mechanical regulation of cell function with geometrically modulated elastomeric substrates, Nature Methods, Vol. 7, pp. 733-739, (2010).
TFM, which operates by mapping forces on the substrate as cells translocate across soft substrates and stretch the substrate, has been used to map forces in the leading vs. retracting edge during cell migration. Despite the usefulness of these methodologies, these techniques are not amenable to simple, high-throughput extraction of contractility measures from mixed populations of cells with rare sub-populations that need high numbers to statistically sample. These types of samples would be seen from a patient sample or mixed culture. Additionally, these previous techniques require high-resolution imaging and precise focusing of optical systems which make them less compatible for high-throughput analysis needed for example in attempting to screen for effect of a large number of drugs on force production. There thus is a need for better methods and systems for identifying and quantifying the forces applied by cells, including populations of cells with rare phenotypes.